It is recognized that add-on bidets should be designed with the following points in mind:
1. The connection of the water supply to an add-on bidet inevitably involves skilled installation work by a competent plumber, but nevertheless the rest of the work of installation of the bidet should be such as to require a minimum of skill and special tools.
2. The designer should see to it that the manual water controls for the bidet are convenient to use, and progressive and controllable in their effect.
3. The bidet should include a movable spray-arm that can adjust from a not-in-use position to an in-use position. In the not-in-use position, the arm should be unobtrusive, or even invisible. The spray-arm must not obtrude into the entry area of the toilet-bowl when the spray-arm is not in use.
4. The water supply to the spray-arm should pass through the spray-arm pivot, so that there is no need for exposed hose-pipes.
5. The bidet includes a seat which can be raised and lowered, and preferably the spray-arm is pivoted onto this seat, rather than for example, onto a housing that remains fixed to the toilet bowl. There is more room on the seat than on the fixed housing to stow the spray-arm when the spray-arm is not in use. Also, again to avoid the use of exposed hose-pipes, the water-supply should pass through the hinge-pivot on which the seat is mounted.